The U.S. Navy's Cryptanalytic Bombe is the culmination of years of work and the efforts of mathematicians and engineers from Poland, England, and the United States. It was the solution to the problem of the German's World War II cipher machine Enigma, and it led to the Allies' successes in the battle of the Atlantic and the war in Europe.
When the United States entered World War II, the British were already breaking and reading many of the German's tactical-level messages enciphered on the Enigma. Their success was a result of the work originally done by Polish mathematicians before the war. Throughout the 1930s Poland's machine, called "Bomba," kept pace with the German's Enigma until shortly before the war broke out. Britain improved on the Bomba and built hundreds of British "Bombes" to continue the effort. However, in 1942 a fourth rotor was added to the U-boat Enigmas and the original British Bombes were not able to find solutions to those messages.
Concerned about shipping losses, the U.S. Navy asked engineers at the National Cash Register Company (NCR) to redesign the Bombe to work against the four-rotor U-boat Enigmas. Within a year, NCR civilians, Navy sailors, and women in the Navy, known as WAVES (Women Accepted for Volunteer Emergency Service) began building and shipping the new Bombes to Washington, DC Between September 1943 and March 1945, 121 Bombes were installed at the Navy's Communications Annex in Washington DC.
The WAVES operated the Bombes working 24 hours a day, 7 days a week. They set the machines up and tested the results. The U.S. Navy Bombes rapidly searched the hundreds of thousands of possible settings on one wheel order of a four-rotor Enigma. (The German Navy had eight wired rotors from which to select three that went into the Enigmas. The fourth rotor remained in its position.) The U.S. Navy Bombes needed to try each combination of rotors until the correct wheel order was found. Fortunately, the machine was so well designed that each run took only 20 minutes, significantly faster than the British Bombes.
There were many different U-boat communication networks, each using a different daily setting. In order to make rapid use of the information that could be derived from decrypted Enigma messages, the Bombes had to find the settings for each network as quickly as possible. On average, settings were found by midday, some more rapidly. The U.S. Navy Cryptanalytic Bombes were so efficient that the British turned the entire U-boat problem over to the United States. Once the Bombes had found the U-boat networks' settings, the Navy Bombes assisted the British with the three-rotor German Army and Air Force Enigma-enciphered messages.
The Navy Bombes, and those who built and operated them, played a crucial role in saving both Allied and Axis lives and hastened the end of the war in the Atlantic and Europe.